Structural-steel joist



J n 2 1927. e N. WAGNER STRUCTURAL STEEL JOIST Filed March 1926 2 Sheets-Sheet 1 NS 'll'flllllllll m \Jm.\\ m UIIIIIEAI IEI Emmi IE l 1927. June N. WAGNER STRUCTURAL STEEL JOIST Filed March 1. 1926 2 Sheets-Sheet 2 i y R I inj'the '30 providing a maximum web clearance Patented June 28, 1927.

UNITED STATES PATENT OFFICE.-

STRUCTURAL-STEEL JOIST.

Application filed larch 1, 1926. Serial H0. 91,583.

- My invention relates to improvements in tructural steel joists and the object of the inventionis to provide a novel type of steel joist in which, by a novel disposition of the component mem ers, for a given strength, the weight is reduced without the use of objectionably light material; a further object is to simplify the design to such an extent that it will affect the cost of fabrication and thus offset any extra cost of steel which it is'necessary to use to insure a durable joist; a further object is to provlde a joist which will lend itself readily to welding of the various connections between the component parts instead of the usual riveted connection; a further object is to provide a joist in which all members thereof are straight and do not require any other work 'before assembling other than sheari a I 120 further object is to provide a joist w fich can be made in any structural steelshop l withont necessitating form of special tools or machine a further-ob 'ect is toprovide a joist, all t e partsof which are readily available stock all structural steelany additional outlayf'lnaterial carried by shops; a. further ob ect is to ellminate the use of the diagonal web members thus facilithe su sequent work or erection by throu h which pipes or conduits may be threa ed more readily and conveniently than where the usual sloping web members are used; a further object is to rovide a joist which will lend itself readl y to the application of a wood floor directly on'top of the joist.

Other objects will appear in the course of the following specification. 40 My invention consists in the construction and a ment of parts, all as hereinafter more particularly described and illustrated in the accompanying drawings in which Fig. 1 is a top plan view of a joist con- 5 structed in accordance with my invention.

Fig. 2 is a side elevation thereof.

F 3 is a section on the lines 33 of Figs. i

Fig. 4 is a section on the lines 4.-4 of Figs. land 2. Fig. 5 consists of a single line diagram in which auxiliary diagonal members shown dotted have been inserted so that a stress diagram may be com let'ed. The loads which are shown in this Egure are the equivalent of an uniform load over the entire span.

Fig. 6 is the stress diagram referred to above.

Fig. 7 shows a system of stresses which are used in my joist as a substitute for the diagonal web members which have been ferent viewsI In the form illustrated, my improved joist I consists of a hori'zontal'top chord l'of channel section and a horizontal bottom chord 2 1 of'angl'e'sectionspaced belowthe to chord. i he b tom: i 1 5 p chord.

chord 2 shorter JConnect-ing'the top aha chords 1 and 2 are a series of spaced apart substantially vertical posts 3 also ,of channel sec- The posts 3 are welded to the top and bottom chords.

Inclined chords 4 are welded to the top chord adjacent to its ends and to the end osts 3 at the bottom thereof so that these l ncslined chords 4 form end members for the 01 Bearing plates 5 are secured to the bottom of the top chord 1 at the ends thereof.

It will be noted that, in my im roved joist all members used are straight an require no yvork before assembling, other. than shearmg, so that the joist may be readily constructed in any structural steel shop without myolving the use of special tools or machmery.

Another feature of my joist is that the top chord can be readily punched if desired for a mailing strip, so that a wood floor may be conveniently attached directly to the steel By the use of vertical posts 3 only, in place of the usual diagonal web members hitherto used, a maximum web clearance is provided which greatly facilitates the subsequent work of erection, as pipes and conduits may be much more conveniently threaded through the joist than is the case when diagonal web membersareuaeiastheeediagonalmem- 13' fthe J here sometimes seriously interfere with the placement of pipes and conduits and considerable work is fr uently involved in keeping clear of such diagonal members particularly where the pipe or conduit is not run- 'veloped :be negligible. Y At some ning perpendicular to the web of the joist.

A further feature of my construction is that pipes or conduits may be readily suspended from the top chord by a hanger, as the concrete floor does not prevent the use of a clip on the bottom of the top chord 1.

It will also be noted that the top chord, being a channel, will carry a substantial concentrated load at any point.

In order to describe the theory used in my novel joist Figures 5, 6, 7 and 8 will be referred to.

Referring now to Fig. 6 we have noted that the vertical component of stress in member 1314 is 1500 pounds and the horizontal component of member 1314 is 2320 pounds.

If the member 1314 is eliminated, as in my joist, these stresses must be accounted for.

Let us now refer to Fig. 7.

Since the diagonal member 13-14 is in tension, the vertical component of 13-14 at the upper end thereof must act downward as shown by force p and the horizontal component must act to the right as shown by force 12 At the lower end of diagonal 1314, the vertical component of 13-14 must act upward as shown by force p and the horizontal component must act to the left as shown by force p Consider now the forces p? and p only.

To counteract these forces we must create a resisting couple of equal and opposite forces such as p and p, p acting in the line of action of. p and p acting in the line of action of p To accomplish this, my joist as illustrated uses a stiif top chord as shown in Fig. 8 and in this manner it is able to develop the resisting couple referred to.

The effect of these resisting internal forces on the top chord is to develop tension in the top flange and compression in the bottom flange adjoining the post '12-13 and compression in the top flange and tension in the bottom flange adjoining the post 1415 as indicated by the plus (compression) and minus (tension) signs in Fig. 8. In other words half of the moment required to resist the moment of the couple p p is developed the remaining half of the moment is dey by the top chord adjoining the post In this discussion I have neglected to con- 'sider:'the' resisting stresses developed by the *bottomchord as their efiect is so small as to point in the top, chord bet-ween posts 1-2'13 and 14-l5 lies the point of conx traflexurewhere no bending moment occurs. taken care of the vertical comresist the couple ponents of diagonal member 13-44 through the stiffness of the top chord, let us now turn our attention to the horizontal components of this diagonal member 13-14 namely.

12 and 12 To resist these We must again create a resisting couple of equal and opposite forces. This time we accomplish this by making our posts stifi' enough to develop these forces.

Referring to Fig. 7 again, it might be noted that p or 12 represents the horlzontal shear across the entire panel. We are therefore justified in making posts 12 -13 and 1415 each assume their share of this shear. To accomplish this we use two forces p" and p to resist 1 also 12 and p to resist 12 The forces 1) and p each of which is equal to of 7 act in the line of action of p but in opposite direction and also forces 12* and 11 each of which is equal to of p? act in the line of action of p but in opposite direction. The forces p" plus 10* form a couple with forces 12 plus p which 17-1 We now make post 1213 still "enough to develop the resisting couple p p and the post 14.15 is made strong enough to develop the resisting couple gi -32 from panel 13-14, plus the resisting couple 1) and p which in turn is developed to resist the horizontal component of diagonal member 15-16 in panel 15-16.

In this way my joist eliminates all diagonal web members by using stiif vertical and horizontal members rigidly connected together to take care of the stresses which are ordinarily developed in the diagonal members commonly used in general construction work.

The axial stress in the top chord as shown in the stress diagram in Fig. 6 can not be neglected. It is therefore necessary to combine the axial stress and bending stress in each panel to find the maximum stress in the top chord.

The axial stress in the bottom chord is assumed to remain a simple tensile stress. No bending stress is figured in combination with it as statedpreviously;

Since the top chord develops the entire vertical components of the resisting stresses it relieves the interior posts of all axial stress.

Since the vertical component of the diag onahweb member (which is eliminated in my oist) represents the vertical shear in the panel, it can readily seen that the vertical shear controls the spacing of the peosts, as the top chord must not bestressed yond the allowable stress for the combination of stresses as previously stated.

The spacing for this type of joist is indicated in Fig. 5. s o r If the bottom chord made stifi, as would be the case if this chord had top and economical however in the shorter spans.

Various modifications may be made in my invention as stated above without departing from the spirit thereof or the scope of the claims and therefore the exact forms shown are to be taken as illustrative only and not in a limiting sense and I desire that only such limitations shall be placed thereon as are imposed by the prior art or are specifically set forth in the appended claims.

' From the foregoing it will be noted that I have devised an improved form of struc tural steel joist which will provide a maximum strength with a minimum Weight of suitable material and whereby the objects of my invention have been attained.

What I claim as my invention is:

1. A structural steel joist of the class described comprising, spaced apart top and bottom chords one of which has top and bottom flanges, and'posts secured to said chords and constituting the entire web system over a portion of the joist, said posts rigidly secured to that chord having top and bottom flanges.

2. A structural steel joist of the class described comprising, spaced apart top and bottom chords and posts secured to said chords and constituting the entire web system for a portion of the joist, the top chord having top and bottom flanges and the posts rigidly secured to said top chord.

NORMAN WAGNER. 

